There has been known a vehicle seat which forecasts a collision from a rear side of a vehicle and moves a head rest of the seat to a forward side by a drive mechanism so as to protect an occupant. In this kind of vehicle seat, for example, as described in Japanese National Publication of Translated Version No. 2004-500273, in the case where the collision is not generated after moving forward, the head rest is moved backward by the drive mechanism, and is returned to a normal position.